[SPARK-14603][SQL][FOLLOWUP] Verification of Metadata Operations by Session Catalog

#### What changes were proposed in this pull request?
This follow-up PR is to address the remaining comments in https://github.com/apache/spark/pull/12385

The major change in this PR is to issue better error messages in PySpark by using the mechanism that was proposed by davies in https://github.com/apache/spark/pull/7135

For example, in PySpark, if we input the following statement:
```python
>>> l = [('Alice', 1)]
>>> df = sqlContext.createDataFrame(l)
>>> df.createTempView("people")
>>> df.createTempView("people")
```
Before this PR, the exception we will get is like
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/pyspark/sql/dataframe.py", line 152, in createTempView
    self._jdf.createTempView(name)
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/lib/py4j-0.10.1-src.zip/py4j/java_gateway.py", line 933, in __call__
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/pyspark/sql/utils.py", line 63, in deco
    return f(*a, **kw)
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/lib/py4j-0.10.1-src.zip/py4j/protocol.py", line 312, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o35.createTempView.
: org.apache.spark.sql.catalyst.analysis.TempTableAlreadyExistsException: Temporary table 'people' already exists;
    at org.apache.spark.sql.catalyst.catalog.SessionCatalog.createTempView(SessionCatalog.scala:324)
    at org.apache.spark.sql.SparkSession.createTempView(SparkSession.scala:523)
    at org.apache.spark.sql.Dataset.createTempView(Dataset.scala:2328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:237)
    at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
    at py4j.Gateway.invoke(Gateway.java:280)
    at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:128)
    at py4j.commands.CallCommand.execute(CallCommand.java:79)
    at py4j.GatewayConnection.run(GatewayConnection.java:211)
    at java.lang.Thread.run(Thread.java:745)
```
After this PR, the exception we will get become cleaner:
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/pyspark/sql/dataframe.py", line 152, in createTempView
    self._jdf.createTempView(name)
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/lib/py4j-0.10.1-src.zip/py4j/java_gateway.py", line 933, in __call__
  File "/Users/xiaoli/IdeaProjects/sparkDelivery/python/pyspark/sql/utils.py", line 75, in deco
    raise AnalysisException(s.split(': ', 1)[1], stackTrace)
pyspark.sql.utils.AnalysisException: u"Temporary table 'people' already exists;"
```

#### How was this patch tested?
Fixed an existing PySpark test case

Author: gatorsmile <gatorsmile@gmail.com>

Closes #13126 from gatorsmile/followup-14684.

2 files changed, 4 insertions, 4 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala
index 21da55cbc3..489a1c8c3f 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala
@@ -87,7 +87,7 @@ class InMemoryCatalog(hadoopConfig: Configuration = new Configuration) extends E
       db: String,
       table: String,
       specs: Seq[TablePartitionSpec]): Unit = {
-    specs foreach { s =>
+    specs.foreach { s =>
       if (!partitionExists(db, table, s)) {
         throw new NoSuchPartitionException(db = db, table = table, spec = s)
       }
@@ -98,7 +98,7 @@ class InMemoryCatalog(hadoopConfig: Configuration = new Configuration) extends E
       db: String,
       table: String,
       specs: Seq[TablePartitionSpec]): Unit = {
-    specs foreach { s =>
+    specs.foreach { s =>
       if (partitionExists(db, table, s)) {
         throw new PartitionAlreadyExistsException(db = db, table = table, spec = s)
       }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
index 54b30d3898..cf9286e6b9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
@@ -111,13 +111,13 @@ class SessionCatalog(
     fs.makeQualified(hadoopPath)
   }
 
-  protected[this] def requireDbExists(db: String): Unit = {
+  private def requireDbExists(db: String): Unit = {
     if (!databaseExists(db)) {
       throw new NoSuchDatabaseException(db)
     }
   }
 
-  protected[this] def requireTableExists(name: TableIdentifier): Unit = {
+  private def requireTableExists(name: TableIdentifier): Unit = {
     if (!tableExists(name)) {
       val db = name.database.getOrElse(currentDb)
       throw new NoSuchTableException(db = db, table = name.table)